The present invention relates to a method and arrangement for detecting a wear limit or break in a cutting edge of a tool having at least one insulated conductor path embedded in its cutting plate and connected with a voltage source so as to form part of a circuit for actuating a signal to break off the machining process.
For an electrically nonconductive ceramic cutter, a system has been proposed for the early detection of a break in the cutting edge according to which a crack in a region of a secondary cutting edge is detected. The detection of such a break interrupts a circuit by destroying a thin conductor path that has been vapor-deposited onto the free secondary face of the tool, thus interrupting the machining process.
This system, up to now, has been used only experimentally. It has not found acceptance in practice because it has considerable drawbacks. In manufacturing processes, electrically conductive workpieces as well as electrically nonconductive workpieces are processed by means of electrically conductive or electrically nonconductive cutting materials, either dry or together with electrically conductive or nonconductive cooling and lubricating agents. It is, therefore, not predictable whether and when in the prior system a current flowing through the circuit is actually interrupted due to the formation of a crack. For example, an electrically conductive bridge may be formed across the crack by particles of the material of the workpiece or the coolant or by particles of an electrically conductive cutting substance and also by contact with the workpiece itself so that, in spite of the fact that the limit of permissible wear has been reached or a break in the cutting edge has occurred, the signal for breaking off the machining process is not initiated.